Steam generating, superheating, and resuperheating plant



STEAM GENERATING, SUPERHEATING, AND RESUPERHEATING PLANT Filed Jan. 21, 1959 May 9, 1961 A. LIEBERHERR 2 Sheets-Sheet 1 5r ELIJWBETH 1?.

El? ADMIN/5773477? ATTO R N EY y 1961 A. LIEDBERHERR 2,983,262

STEAM GENERATING, SUPERHEATING, AND RESUPERHEATING PLANT Filed Jan. 21, 1959 2 Sheets-Sheet 2 5 s" 5 ""5 CONVECTION TCONVECT/O/V CONVECTION:

ZaA/E ZONE ZONE RAD/A 770 RA DIA T'ION I-PAD/A T70 [PAD/A no h ZU/VE n. N NE ..v Z'O VE IN VEN TOR ATTO R N EY United States Patent STEAM GENERATING, SUPERHEATING, AND RESUPERHEATING PLANT Arthur Lieberherr, deceased, late of Winterthur, Switzerland, by Elisabeth R. l eberherr-Amsler, administratrlx, Winterthur, Switzerland, assignor to flulzer Freres, S.A., Winterthur, Switzerland, a corporation of Switzerland Filed Jan. 21, 1959, Ser. No. 788,159

5 Claims. (Cl. 122-478) The present invention relates to a steam generating, superheating and resuperheating plant.

The resuperheater of the plant according to the invention includes a heat transfer apparatus which is placed inside the steam generator for receiving heat from the products of combustion by convection or radiation and in which heat is indirectly exchanged between a high pressure operating fluid, which is heated in tubes forming part of the generator, and the steam to be resuperheated.

The present application is a continuation-in-part application of the copending application Serial No. 485,-

061, filed January 31, 1955, now Patent No. 2,878,791.

The heat transfer apparatus is formed by a group of outer tubes or conduits and a group of tubes disposed inside the outer tubes. If the steam to be resuperheated, which is partly expanded, is conducted through the outer tubes and the high pressure fluid is conducted through the inner tubes, the partly expanded steam exchanges heat with the combustion gases and with the high pressure fluid. If the combustion gases and/or the high pressure fluid are hotter than the steam to be resuperheated, the resuperheating process requires considerably less heating surface and is performed more quickly than in an arrangement in which a part of the heat is indirectly transferred outside of the steam generator from high pressure steam to the steam to be resuperheated, and in which another part of the heat is transferred inside the steam generator from hot combustion gases to the steam to be resuperheated. Radiation losses such as are caused by an indirectly heated resuperheater portion placed outside of the steam generator are avoided with the arrangement according to the invention. No insulation is required for the heat transfer apparatus. Aside from this, no additional space is required outside of the steam generator and pressure losses caused by the high pressure steam pipes connecting an indirect resuperheater with the tubular heating surfaces of the steam generator are eliminated. 'The temperature of the steam leaving the inner tube or tubes of the heat transfer apparatus is considerably higher, if the heat transfer apparatus is exposed to the hot combustion gases than if the apparatus is placed outside of the steam generator, and fuel is saved. The high pressure steam and the low pressure steam may flow in counterflow relation or in the same direction, in contradistinction to heat transfer apparatus arranged outside of the steam generator in which apparatus the high pressure and the low pressure steam must flow in counterflow relation to obtain the desired heat transfer.

The heat transfer apparatus according to the invention may be used for regulating the resuperheat temperature. In this case heating or cooling means and temperature control means are connected with the tubular heating surfaces for the high pressure fluid, so that the high pressure fluid cools the partly expanded steam when 2,983,262 Patented May 9, 1961 the latter is too hot, and heats the partly expanded steam when the latter is too cool.

cases to arrange only one tube inside each outer tube,

particularly if the tubes are-bent in hair pin like fashion. If several hair pin units are connected in series, the heat transfer apparatus may be arranged in zig-zag manner.

If, as in conventional arrangements, the indirect heat transfer apparatus is placed outside of the steam generator, the individual heating tubes of the latter must be connected by means of'a header or collector, and a conduit must be provided to connect the header with a header connecting the individual elements of the indirect heat transfer apparatus. This is unnecessary, if the heat transfer apparatus is arranged inside the steam generator according to the invention, so that pressure losses and cost are reduced. In certain cases, for example, if the temperature of the fluid on one side of the heat transfer apparatus must be controlled by injecting water, the provision of a header may be advisable to interconnect the tube, sections conducting the fluid whose temperature must be controlled. The sections of the tubes conducting the other fluid, however, may be serially interconnected, avoiding headers. Collectors are also desirable, if the different tube sections are not uniformly heated. Since headers for this purpose are usually provided anyway in connection with the tubular heating surfaces of a steam generator, the tubes of individual sections of the heat transfer apparatus arranged according to the invention may be connected in series.

Though in this specification and in the claims the word steam is used to specify the operating fluid of the plant, the invention is not limited'to plants using steam as operating fluid but is equally well applicable to plants using other vapors as operating fluid. The novel features which are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, and additional objects and advantages thereof will best be understood from the following description of embodiments thereof when read in conjunction with the accompanying drawing in which:

Fig. l is a diagrammatic part sectional illustration of a steam plant according to the invention;

Fig. 2 is a diagrammatic part sectional illustration of a modified portion of a steam generator according to the invention;

Fig. 3 is a part sectional diagrammatic illustration of a modification of the part shown in Fig. 2;

Figures 4 to 7 diagrammatically illustrate modifications of the arrangement of the superheater and reheater in the radiation and in the convection zone of the steam generator.

The same numerals designate the same parts in all figures.

Referring more particularly to Fig. 1 of the drawing, numeral 1 designates a steam generator which is heated by a combustion apparatus 2. Numeral 3 designates a combustion chamber in which radiant heat and combustion gases are produced. The combustion gases continue to pass through a flue 4. An operating fluid, such as water, is supplied to the steam generator through an inlet header 5. The water flows through tubes 27 and 7 forming a combustion gas heated feed water preheater, generally known as an economizer. The preheated feed water enters a tubular heating surface 8 which is used for lining the walls of the combustion chamber 3 and is ex- I) posed to radiant heat. The steam formed in the heating surface section 8 is conducted through 'a conduit 9 into a first superheater 10 at least part of which is exposed to radiant heat in the combustion chamber- 3. The superheated high pressure steam'flows .th'rou'ghfa heat transfer apparatus or heat exchanger 11 which will be described later. apparatus 11 passes through a tubular superheating section 12.and therefrom through a steam main 13 into the high pressure part 14 of'a prime mover, such as a steam turbine. The steam. which is partly expanded in theprime mover 14 is conducted through a conduit 15- into a tubular resuperheater section 16 and therefrom into tubes 21 which surround tubes 22 which conduct high pressure steam through the heat transfer apparatus or'heat exchangerll. The resuperheated steam is conducted through a conduit 17 into a low pressure part 18 of the st e am turbine plant. The high pressure turbine 14 and the low pressure turbine 18 have a common shaft for driving an electric generator 19. The steam exhausting from the low pressure turbine 18 is removed through a conduit 20. In'the illustrated embodiment of the'invention, the part of the steam generator, in which heat is transferred by conduction and convection and not by radiation, is too small to accommodate the total required resuperheatiug surface. It is therefore necessary to arrange apart of the resuperheater in the combustion chamber where it is exposed to radiant heat and where it is preferably used for lining a wall portion'of'the combustion'chamber. In the heat transfer apparatuslLithe resuperheating surface is heated by' superheated high pressure steam, as is done in conventional indirectly heated resuperheaters which are arranged outside of .the steam generator and which cause radiation losses. Such losses are avoided with the arrangement according to the present invention. Furthermore, a heat transfer apparatus arranged according to the invention can be much smaller to do the same work as does a conventional steam heated resuperheater.

The heat transfer apparatus 11 includes a plurality of tubes arranged in parallel with respect to the flow of steam therethrough. The plant according to the invention can be so arranged that the superheaters 10 and 12, theresuperheater 16, and the heat transfer apparatus 11 all have the same number of parallelly arranged tubes. The number of headers can thereby be greatly reduced, because each inner tube 22 of the apparatus 11 cangbe connected with a tube of the superheaters 10, 12 for thehigh pressurev steam, and each outer tube 21 can be connected with a tube of the resuperheater 16.- Only the following headers are required: a header 23 at theinlet of the superheater 10, a header 24 at the outlet of-the superheater 12, a header 25 at the inlet of the resuperheater'16, and. a header 26 connected to the outlets of the outer tubes 21 of the heat transfer apparatus 11.

i The feed water preheater or economizer 27, 7 also includes a plurality of tubular elements arranged in parallel with respect to the flow of the fluid therethrou'gh. The part of the economizer formed by the tubes 27 is constructed as a heat'transfer apparatus 6 including outer tubes 27 through which the feed water is conducted, and inner tubes 28 arranged inside the tubes 27 for conducting a-heating fluid which is supplied from a header 29 and returned into a header or collector 30; Theheating fluid is preferably taken from the circuit of the operating-fluid of'the steam plant at a point where the temperature of 'the operating fluid is higher than-that'of'the feed water entering the heat transfer apparatus 6.1 The heatf ing fluid may be steam'bled from the turbine plant." The feed water passing through-the; outer tubes; 27 is thus heated by the inner tubes 28. It'maybeheated simul taneously by the combustion gases passingjoutsidejof the tubes 27 The. combustion gases prevent'in any case heat radiation and losses to the outside. W v.

' Fig. 2 illustrates'a modified arrangement according to The high pressure steam leaving the the invention. The parts of the plant not shown in Fig. 2 correspond 'to the respective parts shown'imFig. 1. Steam produced in the heating surface section 8 of the steam generator is conducted through a conduit 9 and a header 23 into a first superheater 31 from which the superheated steam flows through a header 44, a conduit 32, and a 'header45 into inner tubes 33 of a heat transfer device 34. The high pressure steam leaving the tubes 33 iscollected in a header 46 and passes through a conduit 3S and through an inlet-header 24 into a second superheater '36. 'The high pressure steam superheated in the second superheater 36 is collectedv inv a header 47 and conducted through a steam main 13 to a high-pressure turbine. The partly expanded steam exhausting from the high pressure turbine is conducted through a conduit 15 and a header'25- -int'oi affirstzcoinbhs'tion gas heated resuperheater 37 and therefrom throughouter tubes 38 of the heat transfer apparatus 34; Thepartly expanded steam leaving the tubes 38' is conducted through-a second combustion gas-heated resuperheater 39 at whose outlet a header 26 isprovided rwhich'is-connected,-by means of a conduit 17','with the inlet of a low pressure turbine.

The heat transfer apparatus or heat exchanger 34 constitutesa resuperheater which is heated by high pressure steam'as well as'by combustion gases. In the arrangement illustrated in Fig.2, the combustion-gases heat the partly expanded steam from the outside, whereas the high pressure steam fiowing'through the innertllbes 33 heats the partly expanded steam from the inside; The heat transfer apparatus'cau be used to scrve not only as a resuperheater, 'but'also as a temperature regulator for the steam to be resuperheated. The temperatiue of the high pressure steam can be controlled by injecting water from a conduit 46 into the'high pressure steam conduit 32 which supplies heating steam to the heat transfer device 34, and by injecting water through a conduit 41 into the high pressure steam conduit 35 through which heating steam is removed from the heat transfer apparatus 34. The amount ofwater injected through the conduit 40 into the. conduit 32 is so controlled that the temperature of the steam in the inner tubes 33 is lower or higher than the temperature ofthe partly expanded steam flowing through the outer tubes 38-for coolingor heating; respectively, the partly expanded steam. The

amount of Water injected through conduit 41 into the conduit-35 is controlled to produce the desired. steam temperatureat the outlet of the high pressure superheater 36. A conduit-42 is provided interconnecting the conduits 32 and 35; in which conduit a throttiing means or-valve '43 is arranged'forcontrolling the flow of high pressure steam through the conduit 42. If the high pressure steam is cooled too much in the heat transfer device 34and/or by injection of water from the conduit 40, hot highfpressure steam from conduit 32 can be bypassed through the conduit 42 around the device 34 and conducted into the superheater 36.

I Since the water injection must aifec-t all parallellyarranged tubes of the heat transfer device and of the high pressure stearnsuperheater, headers44, 45, 46, and 47 must be provided in addition to the headers forming part ofthe system shown in Fig. 1. No headers are needed for interconnecting the tubular elements forming the resuperheater heating surfaces 37 and 39 with the outer tubes 33 of the heattransfer device 34.

Fig. 3 illustrates a modification of the heat transfer apparatus forming part of the system according to Fig. 2. If the individual parallelly arranged tubular elements of the heat transfer apparatus 34 and/or of the resuperheaters 37 and 39 are not uniformly heated, the provisionof additional headers 48, 48a, 49, and 49:: maybe advisable. The header 48a mixes'the steam comingfrom the tubes 37, and the header 48 distributes the mixed steam into the'outer" tubes 38. The header-49rmixes the; steam heated in-the tubes 38, and theheader-49,11,dis: tributes the steam into the tubes 39.

Fig. 4 diagrammatically illustrates a modified arrangement of the superheater and reheater section according to the invention. A first part 50 of the high pressure superheater is arranged in the convection zone of the steam generator. The heat transfer apparatus or heat exchanger 51 is also placed in the convection zone; the low pressure steam which is reheated in the apparatus 51 is further heated in a reheater portion which is arran ed downstream of the apparatus 51 and also in the convection zone. The high pressure and the low pressure steam flow in parallel relation through the apparatus 5;. and the high pressure steam leaving the apparatus 51 is superheated to the finally desired temperature in the radiation zone of the steam generator.

Fig. 5 illustrates an arrangement which is like that shown in Fig. 4, the high pressure steam, however, being first heated in the radiation zone of the steam generator before entering the apparatus 51 and being again heated in the convection zone of the steam generator after leaving the apparatus 51. The high pressure steam and the low pressure steam flow in counterflow relation through the apparatus 51.

In the arrangements shown in Figures 6 and 7 the apparatus 51 is in the radiation zone of the steam generator, the low pressure steam, after being heated in the apparatus 51 being further heated by the combustion gases in the convection zone of the steam generator.

In the system shown in Fig. 6 the high pressure steam is heated in the convection zone prior to entering the apparatus 51 and the high pressure steam leaving the latter is further superheated in the radiation zone of the steam generator. High pressure and low pressure steam flow in counterfiow relation through the apparatus 51.

The system shown in Fig. 7 is like that illustrated in Fig. 6 with the exception that the direction of flow of the high pressure steam is reversed so that the high pressure steam and the low pressure steam flow in parallel relation through the heat exchanger 51.

The system according to the invention is particularly useful in connection with a forced flow steam generator of the once-through type. It can be applied to steam or vapor power plants operating at, above, or below the critical pressure of the operating fluid. The elements of the heat transfer apparatus may be arranged in the form of packages or may be arranged in a plane, so that it can be used, for example, for lining or forming the combustion chamber wall or for forming bafiies in large steam generators.

What is claimed is:

1. In a steam generating power plant operating under the reheat cycle and under variable load conditions, a steam generator comprising fuel burning means generating products of combustion, a superheater means having two sections exposed to said products for superheating primary steam, a reheater means exposed to said products for reheating secondary steam, a heat exchanger means having a first tube serially connected to said reheater means for flow of secondary steam through said first tube, said first tube having an outer surface exposed substantially entirely to said products of combustion for heating the secondary steam flowing in said first tube, and a second tube placed inside said first tube, in spaced relation to and longitudinally of said first tube, said second tube being interposed between said two sections for erially connecting said two sections of said superheater means for flow of primary steam in series relation through one of said sections, through said second tube of said heat exchanger means, and through the second section of said superheater means, said first tube and said second tube of said heat exchanger means being organized for heat exchange between the said primary steam flowing throughsaid second tube and the said secondary steam flowing through said first tube and for heat insulation of said second tube by the secondary steam in said first tube against the heat of said products of combustion, heat exchange between said primary steam and said secondary steam being restricted exclusively to said first and second tubes of said heat exchanger means.

2. In a steam generating plant as defined in claim 1, a combustion chamber wherein said fuel burningmeans generate the products of combustion, and a flue connected to and receiving hot products of combustion from said combustion chamber, one section of said superheater means being placed in said line, the second section of said superheater means being placed in said combustion chamber, and said heat exchanger means being placed in said fine.

3. In a steam generating plant according to claim 2 and wherein said second tube of said heat exchanger means is connected to the section of said superheater means which section is placed in said combustion chamher to receive steam from the section which is placed in said combustion chamber, and said second tube of said heat exchanger means is connected to the superheater section which is placed in said flue, for discharging steam into the superheater section which is placed in said flue.

4. In a steam generating plant according to claim 2 and wherein said second tube of said heat exchanger means is 50 connected to said sections of said superheater means as to receive steam from the section placed in said fine and to discharge steam into the section placed in said combustion chamber.

5. In a steam generating plant as defined in claim 1, a combustion chamber wherein said fuel burning means generate the products of combustion, and a flue connected to and receiving hot products of combustion from said combustion chamber, one section of said superheater means being placed in said flue, the second section of said superheater means being placed in said combustion chamber, and said heat exchanger means being placed in said combustion chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,685,279 Caracristi Aug. 3, 1954 2,685,280 Blaskowski Aug. 3, 1954 2,878,791 Lieberherr Mar. 24, 1959 

